--- title: What Is the Summer Solstice? 4 Facts You Should Know description: The 2018 summer solstice, the longest day of the year, starts on June 21. Here's what you need to know, including what time it starts canonical: https://time.com/5314789/summer-solstice-facts/ author: Gina Martinez article:opinion: false article:content_tier: free article:published_time: 2018-06-21T09:00:43.000Z article:modified_time: 2026-05-11T04:57:45.277Z article:section: Science og:title: Today Is the Longest Day of the Year. Here's What to Know About the 2018 Summer Solstice og:description: There are 17 hours of sunlight og:url: https://time.com/5314789/summer-solstice-facts/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltfa3a16e10fddbf7c/6989336a97cdff49e36b5899/summer-solstice-2018-facts.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 4816 og:image:height: 2709 og:image:alt: Summer solstice at Stonehenge og:type: article twitter:card: summary_large_image twitter:title: Today Is the Longest Day of the Year. Here's What to Know About the 2018 Summer Solstice twitter:description: There are 17 hours of sunlight twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltfa3a16e10fddbf7c/6989336a97cdff49e36b5899/summer-solstice-2018-facts.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Today Is the Longest Day of the Year. Here's What to Know About the 2018 Summer Solstice > Sponsored content. 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It reaches 40,000 subscribers with a 34.2% open rate and a 2.1% click rate as of August 2026. #### Where can I follow the energy transition as a business story? Future Proof covers climate and energy as an economic and business story rather than only an environmental one. It publishes every Friday and is free at time.com/newsletters. #### Who writes Future Proof? Justin Worland, a senior correspondent at TIME and an award-winning climate journalist, writes Future Proof. #### Is Future Proof free? Yes. Future Proof is free at time.com/newsletters. by [Gina Martinez](https://time.com/author/gina-martinez/) ## Gina Martinez Jun 21, 2018 9:00 AM UTC  Revellers celebrate summer solstice and the dawn of the longest day of the year at Stonehenge on June 21, 2017 in Wiltshire, England. Revellers celebrate summer solstice and the dawn of the longest day of the year at Stonehenge on June 21, 2017 in Wiltshire, England.Barcroft Media—Barcroft Media via Getty Images by [Gina Martinez](https://time.com/author/gina-martinez/) ## Gina Martinez Jun 21, 2018 9:00 AM UTC While it’s already been hot for weeks, summer doesn’t officially start until the [summer solstice](http://time.com/3928453/summer-solstice-2015/), which falls on Thursday, June 21 this year. The summer solstice, which is the longest day of the year, officially starts Thursday morning in the Northern Hemisphere. During the summer solstice, the sun appears to stand still as it reaches its highest point, before moving off toward the horizon. Here’s everything you need to know about the 2018 summer solstice, including what it means and how Stonehenge is connected to the annual event. ## What is the summer solstice? While the calendar may say June 1 was the first day of summer, the season actually starts [when the summer solstice happens](http://time.com/4825634/summer-solstice-2017/), according to astronomers. That’s because meteorologists divide the year into four seasons based on weather patterns, so the summer solstice always occurs later than the first day of summer on the calendar. The summer solstice begins when the tilt of Earth’s axis is most inclined towards the sun directly above the Tropic of Cancer. The [winter solstice](http://time.com/5075624/shortest-day-year-winter-solstice-sunset-time/), which falls on Friday, Dec. 21 this year, is the exact opposite — when the earth’s axis tilted furthest away from the sun, marking the start of winter.  The sun sets on midtown Manhattan and the Chrysler Building on the summer solstice in New York City on June 21, 2017 as seen from Weehawken, NJ. Gary Hershorn—Getty Images The summer solstice happens every year between June 20 and June 22 when the sun reaches its highest elevation in the Northern Hemisphere, making it the longest day of the year with a stretch of sunlight that lasts for 17 hours. The term solstice derives from Latin word “sol” meaning “sun” and “sistere” which means “to make stand, ” according [Dictionary.com](http://www.dictionary.com/e/summer-solstice/). ## When is the 2018 summer solstice? This year, the summer solstice officially starts at 6:07 a.m. E.T. on Thursday, June 21. And while the summer solstice marks the start of the summer, the days are about to get shorter now because the sun is rising later and setting earlier. ## Is the summer solstice different in the Southern Hemisphere? Yes. For those in the Southern Hemisphere, it is the exact opposite — Thursday’s solstice is actually the shortest day of the year and marks the beginning of winter. In the Southern Hemisphere, the summer solstice falls between December 20 and December 22, the same time period as the Northern Hemisphere’s [winter solstice.](http://time.com/5058769/winter-solstice-2017/) ## How is the summer solstice connected to Stonehenge? One of the most well-known celebrations of [summer solstice is at Stonehenge](http://time.com/4376722/summer-solstice-stonehenge/) in the United Kingdom. Some theories speculate that Stonehenge was specifically designed to align with the sun, according to [Salisbury Stonehenge Tours](http://www.stonehenge-tours.com/blog.Astronomical-Alignments-at-Stonehenge.html). Thousands gather at the prehistoric monument to see the sun rise above the Heel Stone, one of the large stones that is at the entrance of Stonehenge. Both the sunrise of the summer solstice and sunset of the winter solstice align with Stonehenge, creating picture-perfect moments for those who travel there to see it. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/5314789/summer-solstice-facts/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/5314789/summer-solstice-facts/"},"headline":"Today Is the Longest Day of the Year. 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